Direct Measurement of soil natural density
Direct Measurement of soil natural density
(OP)
Hi to all,
I appreciate any comments on insitu methods regarding the direct measurement of soil natural density in deep depths, where no field density test- say by sand bottle- is practical.
Please note that I do not mean indirect estimation by correlation of SPT or CPT values.
Regards
I appreciate any comments on insitu methods regarding the direct measurement of soil natural density in deep depths, where no field density test- say by sand bottle- is practical.
Please note that I do not mean indirect estimation by correlation of SPT or CPT values.
Regards





RE: Direct Measurement of soil natural density
Please exclude the down-the-hole or cross hole tests.
RE: Direct Measurement of soil natural density
Therefore, in you case I would suggest taking 3" diameter Shelby tube samples at the locations where you want/need densities.
RE: Direct Measurement of soil natural density
RE: Direct Measurement of soil natural density
On the other hand, if you have plastic clay that you know to saturated, you can get a pretty decent density from water content and Sp Gr.
Why do you need to know the density more precisely than you can get from correlations? Also, what materials are you dealing with?
RE: Direct Measurement of soil natural density
RE: Direct Measurement of soil natural density
what about the measurements (this method also needs correlation) by gamma ray i.e. the nuclear method?
Is there any possibility to perform the test- and regarding the available apparatus- in deep depths?
Regards
cmorgh
RE: Direct Measurement of soil natural density
Recently, we have had a similar problem as yours at a site comprising uncontrolled, sandy clay fill with some gravel to a depth of over 10m. The fill is currently unsaturated and we wanted to measure the density and density ratio accurately for assessment of potential hydroconsolidation when the water table rises in the future. We tried everything ranging from PMT, SPT and CPT correlated with in-situ density testing in deep (6m) test pits, tube sampling, and down-hole gamma probing.
I am sorry to give you the bad news that none of the above worked. When the material is not saturated, PMT, SPT and CPT resistances are sensitive to moisture content variations, as well as the amount of gravel in the soil matrix. Density from tube samples is easily affected by sampling disturbance as indicated by others. Gamma probing gives wet density only, and is sensitive to uniformity of the hole drilled (i.e. sensitive to size and shape of the hole as may be affected by localised collapse and/or enlargement, and probably also the presence of gravel particles). If you want to try the gamma probe you will at least need to lower the probe down several times at different orientations and also take caliper readings.
So far we have not had any success so I would be pleased to hear from anyone who has a "silver bullet" for this problem.
RE: Direct Measurement of soil natural density
RE: Direct Measurement of soil natural density
RE: Direct Measurement of soil natural density
http://www.rapidimpact.ca/index.htm
Might well work enough to prevent significant collapse on wetting if the fill isn't too wet at present. While on their website, be sure to watch the video of blast densification.
RE: Direct Measurement of soil natural density
If using nuclear device, is there the posibility to lower the probe down to say 25 to 30 m? (regarding the technology of the test and related devices)
The texture I am encountered with is rather non-cohesive. Hence, no traditional sampling would be useful.
Regards
RE: Direct Measurement of soil natural density
I would think that the proximity of the sidewalls of the hole, if close enough, might throw off a nuc. Besides, nucs are not the tool of choice for measuring insitu density of granular material, especially if there are relatively large openwork voids.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
The views or opinions expressed by me are my own and do not necessarily reflect the views or opinions of my employer.
RE: Direct Measurement of soil natural density
Your problem looks more complex. Any collapse tests you could do on samples would be at a "micro" scale (2-4 cm). The gross-scale collapse (of presumably heterogeneous fill) would be a function of the nature of the looser portions and their overall percentage in the 10 m. Can you get reasonably undisturbed samples of the looser material for the oedometer tests? If you measure in-place densities with nuke or something, that would give you density on a different scale, perhaps up to a meter, and you would have to relate it to some reference density that indicates collapse potential. The difference in density between collapsing and noncollapsing materials could be pretty subtle and might be masked by small amounts of gravel in the fill, which would raise the unit weight of the whole soil without affecting the fine-grained matrix where the collapse takes place.
Am I missing something, or is it really that difficult? In part I'm asking out of idle curiosity, but I could run into the same problem on one of our projects since we often run into dry fills in the southwest.
How about an in-situ test with injection wells?
Thanks,
DRG